Landscape composition drives the impacts of artificial light at night on insectivorous bats

Behaviour and landscape contexts determine the effects of artificial light on two crepuscular bird species

Context

Artificial light at night (ALAN) is increasing worldwide, with many ecological effects. Aerial insectivores may benefit from foraging on insects congregating at light sources. However, ALAN could negatively impact them by increasing nest visibility and predation risk, especially for ground-nesting species like nightjars (Caprimulgidae).

Objectives

We tested predictions based on these two alternative hypotheses, potential foraging benefits vs potential predation costs of ALAN, for two nightjar species in British Columbia: Common Nighthawks (Chordeiles minor) and Common Poorwills (Phalaenoptilus nuttallii).

Methods

We modeled the relationship between ALAN and relative abundance using count data from the Canadian Nightjar Survey. We distinguished territorial from extra-territorial Common Nighthawks based on their wingboom behaviour.

Results

We found limited support for the foraging benefit hypothesis: there was an increase in relative abundance of extra-territorial Common Nighthawks in areas with higher ALAN but only in areas with little to no urban land cover. Common Nighthawks' association with ALAN became negative in areas with 18% or more urban land cover. We found support for the nest predation hypothesis: the were strong negative associations with ALAN for both Common Poorwills and territorial Common Nighthawks.

Conclusions

The positive effects of ALAN on foraging nightjars may be limited to species that can forage outside their nesting territory and to non-urban areas, while the negative effects of ALAN on nesting nightjars may persist across species and landscape contexts. Reducing light pollution in breeding habitat may be important for nightjars and other bird species that nest on the ground.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10980-024-01875-3.

Exposure to outdoor artificial light at night increases risk and burden of metabolic disease in Ningxia, China

Nearly a quarter of the world's land has already been polluted by artificial light. And numerous human and animal studies have corroborated that light at night can disrupt metabolism. Therefore, we aimed to estimate the association between outdoor artificial light at night (ALAN) and the presence of metabolic disease. Daily hospital admission cases from Ningxia, China, between 2014 and 2020 were included. Cumulative associations between outdoor ALAN and metabolic disease were estimated using logistic regression and distributed lagged non-linear models (DLNM) with lags of 0-30 days and stratified analysis by age groups and gender. The results suggest that 26.80% of metabolic disease cases in Ningxia can be attributed to outdoor ALAN and that men, especially in men aged 46-59 years, are more susceptible to lighting. Policymakers need to develop measures and facilities in corresponding areas, such as universal access to indoor blackout curtains. In particular, men should be urged to minimize going outside at night and to develop protective measures specifically for men.

Outdoor light at night in relation to glucose homoeostasis and diabetes in Chinese adults: a national and cross-sectional study of 98,658 participants from 162 study sites

AIMS/HYPOTHESIS

Exposure to artificial light at night (LAN) disrupts the circadian timing system and might be a risk factor for diabetes. Our aim was to estimate the associations of chronic exposure to outdoor LAN with glucose homoeostasis markers and diabetes prevalence based on a national and cross-sectional survey of the general population in China.

METHODS

The China Noncommunicable Disease Surveillance Study was a nationally representative study of 98,658 participants aged ≥18 years who had been living in their current residence for at least 6 months recruited from 162 study sites across mainland China in 2010. Diabetes was defined according to ADA criteria. Outdoor LAN exposure in 2010 was estimated from satellite data and the participants attending each study site were assigned the same mean radiance of the outdoor LAN at the study site. The linear regression incorporating a restricted cubic spline function was used to explore the relationships between LAN exposure and markers of glucose homoeostasis. Cox regression with a constant for the time variable assigned to all individuals and with robust variance estimates was used to assess the associations between the levels of outdoor LAN exposure and the presence of diabetes by calculating the prevalence ratios (PRs) with adjustment for age, sex, education, smoking status, drinking status, physical activity, family history of diabetes, household income, urban/rural areas, taking antihypertensive medications, taking lipid-lowering medications, and BMI.

RESULTS

The mean age of the study population was 42.7 years and 53,515 (weighted proportion 49.2%) participants were women. Outdoor LAN exposure levels were positively associated with HbA_1c, fasting and 2 h glucose concentrations and HOMA-IR and negatively associated with HOMA-B. Diabetes prevalence was significantly associated with per-quintile LAN exposure (PR 1.07 [95% CI 1.02, 1.12]). The highest quintile of LAN exposure (median 69.1 nW cm^-2 sr^-1) was significantly associated with an increased prevalence of diabetes (PR 1.28 [95% CI 1.03, 1.60]) compared with the lowest quintile of exposure (median 1.0 nW cm^-2 sr^-1).

CONCLUSIONS/INTERPRETATION

There were significant associations between chronic exposure to higher intensity of outdoor LAN with increased risk of impaired glucose homoeostasis and diabetes prevalence. Our findings contribute to the growing evidence that LAN is detrimental to health and point to outdoor LAN as a potential novel risk factor for diabetes.

Towards a mechanistic understanding of the effects of artificial light at night on insect populations and communities

Artificial light at night (ALAN) is markedly changing the night-time environment with many studies showing single-species responses. Exposure to ALAN can lead to population declines that should have consequences for the functioning and stability of ecological communities. Here, we summarise current knowledge on how insect communities are affected by ALAN. Based on reported effects of ALAN on the interactions between species, and what has been demonstrated for similar effects in other contexts, we argue that direct effects of ALAN on a few species can potentially propagate through the network of species interactions to have widespread effects in ecological communities. This can lead to a shift in community structure and simplified communities. We discuss the diversity of ALAN as a pressure and highlight major gaps in the research field. In particular, we conclude that landscape level impacts on populations and communities are understudied.

A review of the effects of artificial light at night in urban areas on the ecosystem level and the remedial measures

This paper attempts to realize the balance between humans and ecology in designing the nighttime light environment of urban parks by clarifying the influence of nighttime artificial light on the ecosystem of urban parks. Firstly, we reviewed the effects of nighttime artificial light on individual predation and reproduction of animals and personal growth and reproduction of plants. Secondly, we discuss the impact of individual changes caused by artificial lighting on ecosystem function at the ecosystem and analyze its advantages and disadvantages. The results showed that nighttime artificial light had a double-sided impact on the ecosystem, which would hurt the ecosystem function, but had a positive effect on the green space, which lacked natural light and had high plant density. This paper focuses on the areas with increased application of artificial lighting and rich species of animals and plants in night cities, such as urban forest parks and urban green spaces. It discusses how to reduce the intrusion of artificial lighting on ecosystems and how to make better use of the positive effect of artificial light.

Artificial light impacts the mate success of female fireflies

Anthropogenic light pollution is a novel environmental disruption that affects the movement, foraging and mating behaviour of nocturnal animals. Most of these effects are sublethal, and their net impact on reproductive fitness and population persistence is often extrapolated from behavioural data. Without dedicated tracking of wild individuals, however, it is impossible to predict whether populations in light-polluted habitats will decline or, instead, move to shaded refuges. To disentangle these conflicting possibilities, we investigated how artificial light affects mating and movement in North American Photinus, a genus of bioluminescent fireflies known to experience courtship failure under artificial light. The degree to which artificial light reduced mate success depended on the intensity of the light treatment, its environmental context, and the temporal niche of the species in question. In the laboratory, direct exposure to artificial light completely prevented mating in semi-nocturnal Photinus obscurellus. In the field, artificial light had little impact on the movement or mate success of local Photinus pyralis and Photinus marginellus but strongly influenced mate location in Photinus greeni; all three species are relatively crepuscular. Our nuanced results suggest greater appreciation of behavioural diversity will help insect conservationists and dark sky advocates better target efforts to protect at-risk species.

Artificial light impacts the mate success of female fireflies

Anthropogenic light pollution is a novel environmental disruption that affects the movement, foraging and mating behaviour of nocturnal animals. Most of these effects are sublethal, and their net impact on reproductive fitness and population persistence is often extrapolated from behavioural data. Without dedicated tracking of wild individuals, however, it is impossible to predict whether populations in light-polluted habitats will decline or, instead, move to shaded refuges. To disentangle these conflicting possibilities, we investigated how artificial light affects mating and movement in North American Photinus, a genus of bioluminescent fireflies known to experience courtship failure under artificial light. The degree to which artificial light reduced mate success depended on the intensity of the light treatment, its environmental context, and the temporal niche of the species in question. In the laboratory, direct exposure to artificial light completely prevented mating in semi-nocturnal Photinus obscurellus. In the field, artificial light had little impact on the movement or mate success of local Photinus pyralis and Photinus marginellus but strongly influenced mate location in Photinus greeni; all three species are relatively crepuscular. Our nuanced results suggest greater appreciation of behavioural diversity will help insect conservationists and dark sky advocates better target efforts to protect at-risk species.